Determining the domain of in situ stress around Marun Oil Field’s failed wells, SW Iran

Abstract

Accurate determination of the in situ stress domain in oil fields is of paramount importance in drilling, completion, and maintenance of wells and in petroleum geomechanics. Determination of the magnitude and direction of stresses induced by drilling around the wellbores is the first step in geomechanical studies and wellbore stability analyses. Regarding the importance of casing collapse problems in Marun Oil Field, as the first step of this investigation, geomechanical studies were conducted to determine the in situ stress domain in the failed wellbores. Using density measurements, the vertical stress (SV) was estimated to be within the range of 85–90 MPa for all wellbores. To estimate maximum-horizontal-stress (SHmax) domain, Anderson’s faulting theory and stress polygon were employed, and a value close to SV was achieved. Also, minimum horizontal stress (Shmin) was estimated using different approaches and was found to have the minimum in situ stress. Finally, the faulting regime of the areas was found to be normal/strike slip, where the stress values are close to each other due to salt lithology and high pore pressures in the Gachsaran Formation and thereby could be assumed as hydrostatic stresses.